Self-rotating celestial chart with clock drive - uses 24 hour scale rotated in conjunction with star motion to aid astronomical observations

摘要

The star chart providing a direct indication of the hour angle has a cover plate coupled to the drive marked with a 24 hour scale division and rotated in synchronism with the motion of the stars. The cover plate is surrounded by a base plate also having a 24 hour scale division marked around the circumference of the cover plate. Alternatively, the base plate is rotated in synchronism with the movement of the stars. The star chart is used when setting up an astronomical telescope, by providing a direct read-out of the hour angle of the required star at any point during the night.